s390/pkey: Use -ENODEV instead of -EOPNOTSUPP

systemd-modules-load.service automatically tries to load the pkey module
on systems that have MSA.

Pkey also requires the MSA3 facility and a bunch of subfunctions.
Failing with -EOPNOTSUPP makes "systemd-modules-load.service" fail on
any system that does not have all needed subfunctions. For example,
when running under QEMU TCG (but also on systems where protected keys
are disabled via the HMC).

Let's use -ENODEV, so systemd-modules-load.service properly ignores
failing to load the pkey module because of missing HW functionality.

While at it, also convert the -EOPNOTSUPP in pkey_clr2protkey() to -ENODEV.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>